03 Rock Forming Minerals Properties

ROCK FORMING MINERALS

Okki Verdiansyah, M.T.

KULIAH MINERAL OPTIK STTNAS – TGS SEMESTER GANJIL- 2015

1) Rock forming minerals (3x) 2) Secondary / Alteration minerals (1x) 3) Non silicates and opaque minerals (1x) 4) Diskusi dan presentasi mahasiswa (1x)

IGNEOUS ROCKS

Bowen, N. L., 1922, The reaction principle in petrogenesis, The Journal of Geology, Vol. 30, No. 3, pp. 177-198

Norman Levi Bowen (1887 – 1956) paper yg dibuat :

The later stages of the evolution of igneous rocks (1915)

The problem of the anorthosites (1917), Crystallization differentiation in igneous magmas

(1919), Diffusion in silicate melts (1921), Genetic features of alnoitic rocks (1922), The reaction principle in petrogenesis (1922), The behavior of inclusions in magmas (1922), The origin of ultrabasic and related rocks

(1927) The evolution of igneous rocks (1928) [buku]

Igneous Rock : Minerals

• Olivine – Forsterite

– Fayalite

• Pyroxene – Clino : Augite

– Ortho : Hypersthene

• Hornblende

• Biotite

• K-Feldspar – Orthoclase, Microcline, Sanidine

• Plagioclase

• Muscovite

• Quartz

• Magnetite

• Ilmenite

Fungsi Mineral Optik

Identifikasi mineral dengan baik, berupa - Nama mineral

- Tekstur internal kristal (zoning, inklusi, eksolusi)

- Tekstur antar kristal mineral (ofitik, interloking, mozaik, dan lainnya)

- Tekstur diagenesa (alterasi)

Untuk kegunaan lebih lanjut : - Petrogenesis

OCEANIC BASALT VOLCANO SEAMOUNT – INDIAN OCEAN Igneous Petrogenesis

1. Mid-ocean ridges

2. Continental rifts

3. Island Arcs

4. Active continental margins

5. Back-arc basins

6. Ocean Islands

7. Intraplate hotspot activity, carbonatites, or kimberlites

Tholeiites Alkali Basalts

Mid‐ocean ridges, oceanic islands, subduction

zonesOcean islands, subduction zones

Shallower melting (25% melting at <30 km =

tholeiite)

Deeper melting (25% melting at 60 km =

alkaline basalt)

Greater % partial melting ( 30% melting at 60 km =

tholeiite)

Lesser % partial melting (20% melting at 60

km = alkaline basalt)

Fine-grained Coarse

No olivine Olivine common

Quartz, interstitial glass common No quartz; interstitial glass rare

Clinopyroxene (augite, pigeonite) Titaniferous augite (reddish)

Ca-poor orthopyroxene (hypersthene) No orthopyroxene

No alkali feldspar Interstitial alkali feldspar or feldspathoid

Olivine rare, unzoned or orthopyroxene rims Olivine common, zoned

Olivine < plag < augite Olivine < augit < plagio

Orthopyroxene uncommon Orthopyroxene absent

Early plagioclase common Plagioclase less common, appears later

Clinopyroxene = pale brown augiteClinopyroxene = titaniferous augite with

reddish rims

Formation

Groundmass

Phenocrysts

Metamorph

Concept of Index Minerals

Sediment

Sedimentary Rock : Minerals

Feldspar

Quartz

Mafic minerals (pyroxene, amphibole)

Carbonates

Calcite – Dolomite

Fossils

Oxide

Limonite

Clay minerals

Kaolinite, illite, smectite

Lithic (Igneous, Sediment, Metamorph)

Sedimentary rocks

component :

Grains

Matrix

Cement

Pores

Materi RFM Kuliah MO 2015

Olivine

Pyroxene

Hornblende

Biotite

Muscovite

K-Feldspar

Plagioclase

Quartz

Carbonates

Refraction Index : (Indeks Bias)

http://www.uwgb.edu/dutchs/petrology/mintable1.htm

Refraction Index : (Indeks Bias)

CRYSTAL SHAPE

Euhedral

(Demange, M., 2012)

Olivine

forsterite fayalite.

Forsterite – fayalite phase diagram, (Bowen and schrainer, 1932)

Olivine

webmineral.com

Olivine ((Mg,Fe)2Si04) Forsterite (Fo)

Mg2 Si04

Fayalite (Fa)

Fe2 Si04

Sifat Optik Forsterite (Fo) Fayalite (Fa)

Rumus Kimia Mg2 Si04 Fe2 Si04

Sistem kristal

Indeks refraksi

colour (warna) colourless pale yelow

Habit (bentuk)

cleavage (belahan)

fracture (retakan)imperfect, none moderate, none

Pleochroisme (pleokroik) none pale yellow - orange yellow

Relief moderate very high

Birefringe (biasrangkap) δ 0.0330-0.0420 0.0420-0.0510

Int. colour max, (warna terang maks)

Extinction (pemadaman)

Orientation / orientasi X = b; Y = c; Z = a. X = b; Y = c; Z = a

Optic sign (tanda optik) Biaxial (+) Biaxial (-)

2V(Calc)=56-84, 2V(Meas)=74-90 2V(Calc)=54-66, 2V(Meas)=74-47

Ortorombik

nα=1.636 - 1.827

nβ=1.651 - 1.869

nγ=1.669 - 1.879

Equant or slightly elongated prismatic crystals

Tabel perbandingan sifat optik mineral Olivin

Olivine, phenocryst in an Iceland basalt

Olivine ((Mg,Fe)2Si04)

Olivine ((Mg,Fe)2Si04)

c

b

100

Forsterite 84, 2V=90.

Pyroxene

Sifat Optik Ortopiroksen Klinopiroksen

Rumus Kimia (Mg, Fe) 2 Si 2 O 6 (Ca, Mg, Fe(Na, Al, Fe*)) 2 Si 2 O 6

Sistem kristal Ortorombik Monoklinik

Indeks refraksi n: 1.657 - 1.788n: 1.665 - 1.772,

n aegirin : 1.665 -1.826

colour (warna)colourless (pale brown, pale

green, pinkish)

colourless - greenish, purplish

brown

Habit (bentuk)

cleavage (belahan)

fracture (retakan)

Pleochroisme (pleokroik)Pale colored with greenish to

pinkish pleochroism-

Relief moderate moderate-very high

Birefringe (biasrangkap) δ 0.008-0.022 0.023-0.031, 0.034 - 0.052


Extinction (pemadaman) Parallel, symetry Incline

Orientation / orientasi

Optic sign (tanda optik) Biaxial (+)/(-) Biaxial (+)

2Vz : 25 - 70

slightly elongated, prismatic crystals

Two cleavage planes : 87 - 93 at 001, 1 cleaveage at 010,100

Pembeda utama Ortopiroksen dan Klinopiroksen

1) Sudut pemadaman

2) Pleokroisme [biasa hadir pada enstatit]

3) Ortopiroksen mempunyai birefringe (orde 1) lebih rendah dari pada klinopiroksen (orde 2 – 3)

4) Ortopiroksen tidak mempunyai kembaran, seperti klinopiroksen (pigeonit selalu ada kembaran)

Ortho-Pyroxene

Sifat Optik Enstatite Hypersthene

Rumus Kimia MgSiO3 (Mg,Fe)SiO3

Sistem kristal

Indeks refraksi

nα = 1.650 - 1.668

nβ = 1.652 - 1.673

nγ = 1.659 - 1.679

nα = 1.669 - 1.755

nβ = 1.674 - 1.763

nγ = 1.680 - 1.773

colour (warna)colorless, higher Fe contents

correspond to darker colors

colourless (pale brown, pale

green, pinkish)

Habit (bentuk)

cleavage (belahan)

fracture (retakan)

Pleochroisme (pleokroik)

Relief

Birefringe (biasrangkap) δ 0.009 - 0.011 0.011 - 0.018




Optic sign (tanda optik) Biaxial (+) Biaxial (-)

2V:M: 54° to 90°, C: 58° to 86° 2V:M: 70° to 90°, C: 86°

Longitudinal sections will show parallel extinction. Basal sections

will show symmetrical extinction.

prismatic crystals

Ortorombik

moderate - high

Two cleavage planes : 87 - 93 at 001, 1 cleaveage at 010,100

Pale colored with greenish to pinkish pleochroism

Tabel perbandingan sifat optik ortopiroksen

Orthopyroxene - Sample SIC -5. Orthopyroxene seen in the center. Note plagioclase (left of orthopyroxene) with typical twinning. Image by Andrea Gohl. (http://www.science.smith.edu/geosciences)

Opx Opx

A micrograph of an enstatite crystal taken from an ultramatic rock. The thin lamellae of a calcium-rich species, probably pigeonite, have separated from the bronzite; the gray coloration of the host rock betrays its very low calcium content (magnified about 40× [http://www.britannica.com/science/pyroxene

Hypersthene

Sifat Optik Augite Diopside

Rumus Kimia(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6

]CaMgSi2O6

Sistem kristal Monoklin Monoklin

Indeks refraksi

α = 1.680 - 1.735

nβ = 1.684 - 1.741

nγ = 1.706 - 1.774

nα = 1.663 - 1.699

nβ = 1.671 - 1.705

nγ = 1.693 - 1.728

colour (warna)

X= pale green, pa le brown, green,

greenish yel low

Y= pale brown, pa le yel low-green, violet

Z= pale green, grayish green, violet

Habit (bentuk) prismatic crystals

cleavage (belahan)

fracture (retakan)

Two cleavage planes : 87 - 93 at 001, 1

cleaveage at 010,100

Pleochroisme (pleokroik) Visible

Relief high high

Birefringe (biasrangkap) δ 0.026 - 0.039 δ = 0.030


Extinction (pemadaman) Z : c = 35°-48°


Optic sign (tanda optik) Biaxial (+) Biaxial (+)2V:Measured: 40° to 52°, Calculated: 48° to

68°

2V:Measured: 58° to 63°,

Calculated: 56° to 64°

Modification by Verdiansyah, 2015

Tabel perbandingan sifat optik antara Augit dan Diopsid

Augite (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6

Section c

(100) Section

(010) Section

c

a

b

Augite

Ortho – clinopyroxene intergrowth

Pyroxene

Amphibole

Hornblende

Amphiboles & Pyroxenes

Hornblende ((Na,K)0-1Ca2(Mg,Fe,Al)5 (Si,Al)8O22(OH)2)

Sifat Optik Ferro Hornblende Magnesio Hornblende

Rumus Kimia {Ca2}{Fe42+Al}(AlSi7O22)(OH)2 {Ca2}{Mg4Al}(AlSi7O22)(OH)2

Sistem kristal Monoklin Monoklin

Indeks refraksinα = 1.687 - 1.694

nβ = 1.700 - 1.707

nγ = 1.701 - 1.712

nα = 1.616 - 1.680

nβ = 1.626 - 1.695

nγ = 1.636 - 1.700

colour (warna)

Habit (bentuk)

cleavage (belahan)

fracture (retakan)

Pleochroisme (pleokroik)

strongly pleochroic :

Pleochroism (x): deep brown or pale greenish

brown.

Pleochroism (y): straw yellow or dark greenish

brown.

Pleochroism (z): yellow or bluish green.

strongly pleochroic :

x: l ight green, yellowish green, yellow,

greenish brown, or yellow

y: dark green, dark yellowish green,

brown. Pale, reddish brown, or

greenish yellow

Relief high Moderate

Birefringe (biasrangkap) δ δ = 0.014 ‐ 0.018 δ = 0.02




Optic sign (tanda optik)

2V:Measured: 12° to 76°, Calculated: 30° to 62°2V:Measured: 66° to 85°, Calculated: 58° to

88

prismatic crystals

Usually strongly coloured in green, yellow-green, blue-green and brown.

Two: perfect prismatic [110] at 124 degree

12 - 34

Biaxial (-)


Quiz Identifikasi piroksen dan olivin :

(Demange, M., 2012)

Sediment

Sedimentary Rock : Minerals

Feldspar

Quartz

Mafic minerals (pyroxene, amphibole)

Carbonates

Calcite – Dolomite

Fossils

Oxide

Limonite

Clay minerals

Kaolinite, illite, smectite

Lithic (Igneous, Sediment, Metamorph)

Sedimentary rocks

component :

Grains

Matrix

Cement

Pores

Ammonite. Polarised light micrograph of a thin section through a fossilised ammonite, a type of shelled mollusc that lived around 200 million years ago. Crystals of calcite and quartz have developed in the spiral cavity of the ammonite's shell. Magnification x6 at 4x5ins size. (http://fineartamerica.com/---)

CARBONATES

CARBONATES

Kalsit

Aragonite

Rodokrosit

Siderite

Magnesit

http://www.mindat.org/

Dolomit

Ankerit

Kalsit

Sifat Optik Calcite Aragonite Dolomite

Rumus Kimia CaCO3 CaCO3 CaMg(CO3)2

Sistem kristal Trigonal Orthorhombic Trigonal

Indeks refraksinω = 1.640 - 1.660

nε = 1.486

nα = 1.529 - 1.530

nβ = 1.680 - 1.682

nγ = 1.685 - 1.686

nω = 1.679 - 1.681

nε = 1.500 - 1.503

colour (warna) colourless colourless colourless

Habit (bentuk)usually rhombohedral crystals when

euhedral

Usually radiating or columnar

elongate grainsOften as rhombohedral crystals

cleavage (belahan)

fracture (retakan)Three: perfect rhombohedral [101] One: imperfect cleavage [010] Three: perfect rhombohedral [101]

Pleochroisme (pleokroik) - - -

Relief Negative, Low, Moderate, High Negative, Low, Moderate Negative, Low, Moderate, High

Birefringe (biasrangkap) δ 0.154 - 0.174 0.156 0.179 - 0.182


Extinction (pemadaman) Parallel


Optic sign (tanda optik) Uniaxial (-) Biaxial (-) Uniaxial (-)2V: Measured: 18° to 19°, Calculated: 16° to 18°


Tabel perbandingan sifat optik mineral karbonat

Dolomite (CaMg(CO3)2)

Large botryoid of aragonite (A) from a stalagmite from Madagascar. Dark area in botryoid (red double-pointed arrow) is due to extinction of vertical crystals in cross-polarized light. Termination of crystals in right side of A against smaller cluster at right (a) suggests that the smaller cluster grew first and blocked growth of A in that direction. Black areas (V) are void space; truncation of aragonite crystals (e.g., white arrow) suggests that some or much of that void space is the result of dissolution of aragonite.

Aragonite (CaCO3)

Calcite (CaCO3)

BATUAN KARBONAT

Koesoemadinata, 1981

From left to right: Halimeda, Penicillus, Udotea, Rhipocephalus.

Halimeda

GREEN ALGAE

Mizzia sp

RED ALGAE

A crustose coralline red algal

possible segmented red alga

Mazloviporidium sp. (syn. Cribroporidium, Contortoporidium)

FORAMINIFERA

calcareous uniserial benthic foraminifer in a ferruginous hardgroun

biserial foraminifer (probably Of the genus Deekerella)

Archaeocyath

(sponges)

chambered calcareous sponge forming part of the framework of this world-renowned reef complex.

Carbonates Mud

Definitions:

• Micrite - An abbreviation of “microcrystalline calcite”. The term is used both as a synonym for carbonate mud (or “ooze”) and for a rock composed of carbonate mud (calcilutite). Micrite consists of 1 to 4 µm-diameter crystals and forms as an inorganic precipitate or through breakdown of coarser carbonate grains. Micrite is produced within the basin of deposition and shows little or no evidence of significant transport (Folk, 1959).

• Microspar - Generally 5- to 20-µm-sized calcite produced by recrystallization (neomorphism) of micrite; can be as coarse as 30 µm (Folk, 1965). Restricted to recrystallization products, not primary precipitates.

• Pseudospar - A neomorphic (recrystallization) calcite fabric with average crystal size larger than 30-50 µm (Folk, 1965).

Keys to Petrographic Recognition:

1) Modern carbonate mud consists largely of the breakdown products of organisms (due to decomposition of organic binding materials and abrasion or maceration of shells). Macroscopic algae (especially green algae) are major contributors of needle-shaped, mud-sized, aragonitic particles in tropical platform and platform margin settings. Modern inorganic aragonitic precipitates, in the water column or on the seafloor, also are needle-like (with individual crystals typically 3-5 µm in length) and may contribute to carbonate muds.

2) The calcitic micrite of older carbonate rocks was neomorphically formed from mixed mineralogy precursors to form an equant mosaic of 1- to 4-µm crystals. The precursor material acted as detrital particles and so may show geopetal fabrics, scattered coarser particles, and other indications of mechanical sedimentation. Inclusions or molds of precursor minerals may be seen within micritic calcites (especially using SEM).

3) Neoformed microcrystalline cement and microbial precipitates may show clotted or peloidal fabrics and can grow in any position within interparticle pores or larger cavities (non-geopetal fabrics).

4) Microspar and pseudospar typically have patchy distributions grading into normal micrite; crystal outlines tend to be elongate (loaf-shaped) or have irregular, sutured boundaries).

Scholle, 2003

Carbonate mud (micrite) fills the lower part of the cavity while sparry calcite fills the upper part — the contact indicates an approximately level surface at the time of deposition

Here replacive calcite spar has embayed the originally smooth margins of a reworked (and thus substantially lithified) micritic intraclast

precipitated spar (the clear, coarse spar) and microspar formed by neomorphism of micritic matrix

sparsely fossiliferous micrite consists of a mix of nannoconids and other micritic material, including other finely comminuted skeletal particle

Micrite & Sparite

Micrite

Carbonate mud is termed micrite (0.03-0.04 mm)

Micrite can also form as a cryptocrystalline cement in certain circumstances.

Because of this it must be used with care as an index of depositional energy.

In conclusion, it would appear that lime mud, micrite, can form by a variety of processes.

Cement.

By definition this applies to crystal- line material that grows within the sediment fabric during diagenesis.

The most common cement in limestones is calcite, termed "spar" or sparite

Other cements in carbonate rocks include dolomite, anhydrite, and silica.

(x40) (D) Skeletal fragment with advanced calcite cementation. Sparry crystals have grown, with increasing size, both into the intergranular pores, and into the biomoldic pore caused by the solution of the orginal aragonite shell. (x60)

(A) Lime mudstone. Chalk, Upper Cretaceous, Beer, Devon. (x60)

(Selley, 2000)

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03 Rock Forming Minerals Properties